|
|
Post by q8 on Sept 12, 2005 11:24:40 GMT
 Can somebody tell me how LED'S actually work? I assume they are low voltage but how is the light actually created?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 12, 2005 11:42:23 GMT
I think we're getting into quantum physics here. I read an explanation once and it made my brain hurt.
They run off low voltage; they come in a number of pretty colours; if you don't exceed the specified voltage they last indefinitely; and they create much less heat than ordinary light bulbs.
When they are used in signals, red ones mean you stop and green ones mean you go. A series of white ones at an angle mean you may or may not be about to go down the correct line.
|
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,762
|
Post by Chris M on Sept 12, 2005 11:43:45 GMT
|
|
|
|
Post by q8 on Sept 12, 2005 11:50:54 GMT
When they are used in signals, red ones mean you stop and green ones mean you go. A series of white ones at an angle mean you may or may not be about to go down the correct line.
------------------------------------------------------------------------
Nick, why don't you get a job as a comedian? You'd go down a riot at a an undertakers convention. ;D
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 12, 2005 11:57:25 GMT
When they are used in signals, red ones mean you stop and green ones mean you go. A series of white ones at an angle mean you may or may not be about to go down the correct line. ------------------------------------------------------------------------ Nick, why don't you get a job as a comedian? You'd go down a riot at a an undertakers convention. ;D I think the Wikpedia article proves my point about heads hurting. And my quoted bit is really all one needs to know...  |
|
|
|
Post by piccadillypilot on Sept 12, 2005 12:39:03 GMT
Can somebody tell me how LED'S actually work? I assume they are low voltage but how is the light actually created? Here's an article on the workings of LEDs. www.pctechguide.com/07panels_LEDs.htm |
|
Phil
In memoriam
RIP 23-Oct-2018
Posts: 9,473
|
Post by Phil on Sept 12, 2005 22:21:58 GMT
Can somebody tell me how LED'S actually work? I assume they are low voltage but how is the light actually created? Here's an article on the workings of LEDs. www.pctechguide.com/07panels_LEDs.htmIt's a shame even Firefox and Panda couldn't stop the popup (with integrated spyware) when this link was opened |
|
|
|
Post by piccadillypilot on Sept 12, 2005 22:27:33 GMT
It's a shame even Firefox and Panda couldn't stop the popup (with integrated spyware) when this link was opened Using Firefox here, no popup. |
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,762
|
Post by Chris M on Sept 12, 2005 23:39:44 GMT
It's a shame even Firefox and Panda couldn't stop the popup (with integrated spyware) when this link was opened Using Firefox here, no popup. Same here - firefox 1.0 with popups disabled + adblock = no popups. Chris |
|
|
|
Post by q8 on Sept 13, 2005 1:35:13 GMT
Two questions regarding these things. Would LED's be bright enough to replace headlights? and could they be used to illuminate car interiors?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 13, 2005 2:52:56 GMT
You can buy LED replacements for household low-voltage halogen downlights, so you can certainly get them bright enough for car interiors. You would need a resistor in series to drop the 12V down to a voltage suitable for the LED. About a year ago, Australia's only electronics magazine, Silicon Chip, published an article on how to use LEDs to replace ordinary bulbs in car stop lights and interior lights.
As for headlights, they may now be bright enough: there are good LED torches available. But (a) they would be more expensive than the current halogen bulbs; and (b) there might be problems in getting them to dip, which is easy with conventional headlight bulbs.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 13, 2005 4:09:18 GMT
Two questions regarding these things. Would LED's be bright enough to replace headlights? and could they be used to illuminate car interiors? There are mainline trains which use white LED's for headlights now. If you see this photo you can clearly see the LED clusters for head and tail lights. Obviously LUL are also using LED's to replace the tail lights on the C&D stocks (see Solidbond's pic on Dave's main site.) |
|
|
|
Post by q8 on Sept 13, 2005 7:29:53 GMT
The reason I asked if LED's could replace train headlights is that the 'glare' problem in tunnels could be eliminated. If they work at less that 12v what voltage do they use?
If they are bright enought to illuminate car interiors it would be preferable to the 'cold' glare of fluorescent tubes. (May be cheaper too)
|
|
|
|
Post by Dmitri on Sept 13, 2005 8:45:44 GMT
If they work at less that 12v what voltage do they use? Approximately from 2 V for the red ones to the 3.5-4 V for the white ones. More precisely, LEDs should be fed from the current source, not from the voltage source, because voltage drop on them remains almost the same regardless of the current flowing through (a characteristic feature of p-n junctions). If you need brighter light you may take as many of them as you wish  . |
|
|
|
Post by igelkotten on Sept 13, 2005 9:28:07 GMT
If they are bright enought to illuminate car interiors it would be preferable to the 'cold' glare of fluorescent tubes. (May be cheaper too) Daylight-temperature LEDs are, from what I know, very expensive. They are, however, used for emergency lightning and spotlighting, as well as in hand-held torches. High-intensity LEDs are more expensive than light bulbs, but should last significantly longer. They may also need a bit more lensework to get a beam with good characteristics (coherent focus, soft edges, even light throughout the cone etc). For example, this little baby is what I have dangling in my keyfob: www.uwkinetics.com/UK2AAAWLEDIND.htm |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Sept 13, 2005 9:56:02 GMT
More precisely, LEDs should be fed from the current source, not from the voltage source True, but a resistor and a LED in series across a constant DC voltage will pass a constant current. A dropper resistor is the usual way of running LEDs in consumer equipment, because it's cheaper than a constant current source and works just as well. |
|
|
|
Post by Dmitri on Sept 13, 2005 10:51:25 GMT
A dropper resistor is the usual way of running LEDs in consumer equipment, because it's cheaper than a constant current source and works just as well. Surely - a dropper resistor may be treated as a low-cost current source . |
|
Can somebody tell me how LED'S actually work? I assume they are low voltage but how is the light actually created?
.
